Microbial diversity of consumption milk during processing and storage

• Published in: International journal of food microbiology 2018-02, Vol.266, p.21-30
• Main Authors: Porcellato, Davide, Aspholm, Marina, Skeie, Siv Borghild, Monshaugen, Marte, Brendehaug, Johanne, Mellegård, Hilde
• Format: Article
• Language: English
• Subjects: Abundance; Bacillales; Bacillus cereus; Bacteria; Cartons; Cow's milk; Culture techniques; Dairies; Dairy industry; Gene sequencing; Microbiota; Microorganisms; Milk; Milk microbiota; Milk quality; Milk storage; Pasteurization; Pasteurized milk; Product safety; Pseudomonadales; Quality assurance; Raw milk; Risk assessment; rRNA 16S; Seasonal variations; Shelf life; Storage; Storage temperature
• ISSN: 0168-1605; 1879-3460
• DOI: 10.1016/j.ijfoodmicro.2017.11.004

Bovine milk contains a complex microbial community that affects the quality and safety of the product. Detailed knowledge of this microbiota is, therefore, of importance for the dairy industry. In this study, the bacterial composition of consumption milk was assessed during different stages in the production line and throughout the storage in cartons by using culturing techniques and 16S rRNA marker gene sequencing. Monthly samples from two dairies were analyzed to capture the seasonal variations in the milk microbiota. Although there was a core microbiota present in milk samples from both dairies, the composition of the bacterial communities were significantly influenced by sampling month, processing stage and storage temperature. Overall, a higher abundance of operational taxonomic units (OTUs) within the order Bacillales was detected in samples of raw and pasteurized milk from the spring and summer months, while Pseudomonadales and Lactobacillales OTUs were predominant in the winter months. OTUs belonging to the order Lactobacillales, Pseudomonadales, Clostridiales and Bacillales were significantly more abundant in milk samples taken immediately after pasteurization compared to raw milk samples. During storage of milk in cartons at 4°C, the bacterial composition remained stable throughout the product shelf life, while storage at 8°C significantly increased the abundance of OTUs belonging to the genus Bacillus and the plate count levels of presumptive Bacillus cereus. The knowledge obtained in this work will be useful to the dairy industry during their quality assurance work and risk assessment practices. •Season, processing and storage temperature significantly influenced the milk microbiota.•Bacillales OTUs predominated in raw milk during the spring and summer months.•Pseudomonadales and Lactobacillales OTUs predominated in the winter months.•Storage of milk cartons at 8°C increased the relative abundance of Bacillus OTUs compared to storage at 4°C.•A correlation between the levels of Bacillus in raw milk and milk stored in carton was detected.